High performance washing machines use variable speed motors, such as induction motors, that are required to operate over a wide speed range of approximately 30 to 1. During the wash cycle, the motor operates at a low speed typically in the range of 400-800 rpms with high torque. During the spin cycle, the motor operates at a high speed, typically in the range of 12,000-18,000 rpms with low torque. In order to deliver the necessary torque and speed, the motor has its windings in a delta (Δ) configuration. This results in a motor which has operating parameters requiring high currents and low voltage during wash cycles, while having lower currents and higher voltage during spin cycles. Such operating parameters result in requiring a motor drive circuit with a large volt-amp or horsepower capability.
Flux weakening techniques and tapped windings have been used to reduce the volt-amp requirement of the motor drive circuit. Such techniques and windings have an impact on the manufacturing costs and the output performance characteristics of the motor.